The TV couple who ruled for much of the '80s, Bill Cosby and Phylicia Rashad, are reunited tonight on a new episode of "The Cosby Mysteries" -- although it's no mystery why their reunion is occurring now. It's sweeps month. Also tonight: The return of "Sister, Sister," the continuation of "Scarlett" and the conclusion of "JFK."
* "The Cosby Mysteries" (8 p.m.-9 p.m., Channel 2) -- This episode prefigures what is likely to be the crux of the O. J. Simpson trial: dueling forensic experts. In tonight's murder case involving a rich financier (is there any other kind?), it's Guy Hanks (Mr. Cosby) for the defense, and Hadley Roebuck (Ms. Rashad) as a witness for the prosecution. NBC.
* "Sister, Sister" (8 p.m.-8:30 p.m., Channel 13) -- This sitcom was the least offensive of ABC's TGIF lineup, partly because adults could enjoy the comedy of Jackee Harry and Tim Reid while kids enjoyed the identical twin teens (Tia and Tamara Mowry) around whom the show is designed. Back for a second season, "Sister, Sister" is worth sampling -- especially opposite "The Boys Are Back" on CBS, which wastes talents of Suzanne Pleshette and Hal Linden. ABC.
* "JFK" (9 p.m.-11 p.m., Channel 2) -- Part 2 of 2. Sunday's opening installment of this 1991 Oliver Stone movie contained the most laughably inept dialogue looping I've ever heard. While Kevin Bacon's character was swearing up a storm, the edited-for-TV version seeded that storm and turned it into a drizzle. An impolite word for sphincter, for example, became "eyeball," and that was the least absurd of the many euphemisms. NBC.
* "Scarlett" (9 p.m.-11 p.m., Channel 11) -- Part 3 of 4. If you've stayed with the story this long, this is the night that investment reaps its modest but worthwhile rewards. In other words, the plot finally thickens. Joanne Whalley-Kilmer, Timothy Dalton star. CBS.
* "Starry, Starry Night" (9 p.m.-10 p.m., Channels 22, 67) -- Maryland Public Television turns its telescope on the stars that have sparkled in MPT productions in the past 25 years. "Night" features highlights from "In Performance at Wolftrap," "Great Performances," "The BSO Salutes Maryland" and other shows while hailing Marylanders who have made the big time. PBS.
* "Help Not Wanted" (10 p.m.-10:30 p.m., MTV) -- This is a #F straight-on, sometimes bleak look at job prospects for the current generation of college graduates, high-schoolers and dropouts. Tabitha Soren is host.
* "Tales From the Crypt" (11 p.m.-11:30 p.m., HBO) -- Of all the original EC Comics "Crypt" tales, this is the one I remember the most: It's the one in which blind tenants get even, in justified yet horrible fashion, with their heartless landlord. Anthony Zerbe, Teri Polo star.